How to add sudo user in linux?

1. #useradd test123
2. #usermod -G wheel -a test123 //add user to wheel group

3. Uncomment following in /etc/sudoers file :

# Uncomment to allow people in group wheel to run all commands
%wheel ALL=(ALL) ALL

4. Add user john in /etc/sudoers file :

# User privilege specification
root ALL=(ALL) ALL
test123 ALL=(ALL) ALL

test123 can run customized commands too.

Try :)